This invention relates to apparatus for treating suspensions and more particularly relates to apparatus for treating suspensions of papermaking stock prior to delivery of such stock to a point of use, e.g., a papermaking machine.
The current trend in the papermaking industry is in the direction of larger and higher operating speed systems. As machine size and speed increases, it becomes necessary to provide a larger number of small cleaners in the system to classify or clean the papermaking stock before it is delivered to the paper forming machine. Desirably, such stock also is subjected to a deaeration operation generally concurrent with the cleaning operation since as is well known, deaeration contributes considerably to the quality of the formed paper product. Representative of apparatus involving both cleaning and deaeration is the disclosures of U.S. Pat. Nos. 3,432,036; 3,538,680 and 3,720,315. However, the requirement for providing additional numbers of cleaners in a papermaking system also presents the problem of increased energy demand for operating the cleaners particularly with respect to overcoming the frictional losses encountered in supplying feed from a source of stock to and through the cleaners. Moreover, there is the problem associated with where such cleaners conveniently can be mounted in the system, i.e., the availability of such additional space in the mill as is required to allow for mounting or integrating the cleaners within the system. Furthermore, where a great number of cleaners are employed in a papermaking system, the need to conveniently and quickly remove defective or plugged cleaners from the system places a limitation on the manner in which such cleaners can be mounted on or adjacent to a central stock collection receiver into which is feeding accepted stock discharge from the cleaner units.
Canister arrangements or close grouping of cleaners in a system are known in the prior art. However such cleaners are not arranged in the natural attitude for such cleaning, i.e., in a generally vertical positioning. Instead, cannister cleaners are arranged in a horizontal attitude as, for example, in the fashion of the spokes of a wheel. Thus such cleaners are not self-draining and during system shutdown stock lays in the cleaners with the consequence that fiber builds up in the cleaners to the disadvantage that such condition promotes cleaner clogging when the system is restarted.
Each of the problems and circumstances above enumerated are ameliorated by the present invention, as will be apparent from the description which follows.